The patient is a 40-year-old male who presented with weakness in both the upper and lower limbs for 3 days. Laboratory tests showed hypokalemia, metabolic alkalosis, hypomagnesemia, and increased urinary excretion of potassium, sodium, and chloride. Based on these findings, the nephrologist diagnosed the patient with Gitelman's syndrome, a genetic disorder characterized by loss of potassium, sodium, magnesium, and chloride in the urine.